A mass mailing system generally comprises a mail inserting machine and a mail stacking machine. The mail inserting machine includes an envelope feeder and an enclosure document supply section. The envelope feeder is used to feed envelopes, one at a time, to an envelope insertion station. In the enclosure document supply section, a plurality of enclosure feeders is used to release enclosure documents to a chassis. The released documents are then gathered, collated and pushed by a plurality of pusher fingers to the envelope insertion station for insertion. Mail inserting machines are known in the art. For example, Roetter et al. (U.S. Pat. No. 4,169,341) discloses a mail inserting machine wherein documents are released onto a continuous conveyor mechanism to be collected and collated in a continuous matter. After the enclosure documents are inserted into the envelopes, the filled envelopes are typically transported to another piece of equipment that seals the envelopes and affixes postage or prints a postage indicium on each envelope.
The filled envelopes are typically collected and loaded by an operator into mail trays or other forms of storage. This step in the mass mailing process has been found to be a “bottleneck”. One way to assist the operator in eliminating the bottleneck is to use an envelope stacking machine to automatically collect the filled envelopes into a stack so that the operator can remove the filled envelopes in stacks. One of the commonly used envelope stackers is an on-edge stacking apparatus. For example, Keane et al. (U.S. Pat. No. 6,398,204) discloses a mail stacking machine where a belt turn-up unit is used to turn the filled envelope from a horizontally facing direction to a vertical or “on-edge” position. The vertically oriented envelope is driven by a segmented roller into the bottom of a vertical stack.
A typical stacking machine 1, as shown in FIG. 1, comprises a mailpiece input device 30, an incoming mailpiece moving device 40 and a stacking deck 50 having a first side 56 and a second side 58. As shown in FIG. 1, the stacking deck 50 has a deck surface 52 to support a stack of mailpieces 20. An incoming mailpiece 10, which enters the stack deck 50 from the input device 30 along a direction 110, is driven by the moving device 40 into the bottom of the stack 20. As more mailpieces 10 are added to the bottom end 24 of the stack 20, the stack 20 expands or grows toward the downstream end of the stacking deck 50. As the stack 20 expands, the pressure on the incoming envelope 10 increases. In order to relieve the stack pressure, a continuous conveyor belt 54 moving along a direction 120 is used to space out the stacked mailpieces, thereby making room for the next incoming mailpiece 10 to join the stack 20. At the same time, a paddle 60 is used to support the front end 22 of the stack 20, preventing the top mailpieces of the stack 20 from falling toward the downstream end. The paddle 60 is linked to a bearing collar 64 by a handle 62. The collar 64 is movably mounted over a shaft or support rod 66 for movement. The support rod 66, which is substantially parallel to the moving direction 120, is fixedly mounted on rod mounts 68.
As shown in FIG. 2, the mailpiece input device 30 has an input end and an output end. If the mailpiece 10 enters the input end of the mailpiece input device 30 in a horizontal orientation, it is possible to use a belt turn-up mechanism to change the orientation of the mailpiece 10 when it emerges from the output end. As shown, the belt turn-up mechanism comprises two inner rollers 34 and two exit rollers 36. The input rollers 34 and the exit rollers 36 are linked together with two continuous belts 32, 33 to form an input nip 134 at the input end and an exit nip 136 at the output end. The input nip 134 formed by the input rollers 34 and the belts 32, 33 receives a flat mailpiece 10 oriented in a generally horizontal direction. The exit nip 136 formed by the output rollers 36 and the belts 32, 33 drives the mailpiece 10 out of the input device 30 in a generally vertical direction so that the mailpiece 10 can be stacked in an on-edge stacker. As shown, the rollers 34, 36 are operatively connected to a motor 80 to move the belts 32, 33. A belt turn-up mechanism is known in the art (see Keane et al.).
In the on-edge stacker as disclosed in Keane et al., the incoming mailpiece moving device 40 comprises a segmented roller 42 and an intake roller 44 to move an incoming mailpiece 10 into the stack 20. As shown, the moving device 40 has a registration wall 48 to stop the leading edge of the incoming mailpiece 10 in order to align the incoming mailpiece 10 with other mailpieces in the stack 20. As shown in FIG. 3a, the segmented roller 42 has a flat, planar surface segment 142 and a curved or cylindrical surface segment 144. The planar surface segment 142 can be viewed as a cutoff segment of a cylinder. These segments meet with each other and form two edges: an inner edge 148 and an outer edge 146. When the segmented roller 42 is at rest at its home position, the inner edge 148 of the segmented roller 42 pushes the bottom end 24 of the mail stack 20 frontward to make room for the next mailpiece 10 to join the stack 20. As such, the incoming piece 10 can be driven by the rollers 36 along the direction 110 into the gap between the bottom of the mail stack 20 and an input guide 46. The planar surface segment 142 is typically a smooth, lubricous plastic surface so as not to hinder the movement of the incoming mailpiece 10. When the mailpiece 10 enters into the “throat” 242 formed by the flat surface segment 142 of the segmented roller 42 and the bottom of the mail stack 20, as shown in FIG. 3b, the segmented roller 42 is caused to rotate in a clockwise direction 150 in a continuous, one-part motion to drive the incoming mailpiece 10 toward the intake roller 44. The segmented roller 42 continues to drive the incoming mailpiece 10, as shown in FIGS. 3c and 3d, until the leading edge of the mailpiece 10 registers with the registration wall 48. The segmented roller 42 continues to rotate until it reaches its home position, as shown in FIG. 3a. For driving purposes, the cylindrical surface segment 144 of the segmented roller 42 typically has a highly frictional, elastomeric covering over the circumference.
This one-part movement of the segmented roller 42 may not work satisfactorily at high processing speeds, partly due to the variation in the arrival time of the incoming mailpiece 10. For example, when the motor 80 is cold, it has a lower speed than its average speed. Consequently, the segmented roller 42 may rotate before the incoming mailpiece 10 reaches a desired position in the gap between the exit nip 134 and the throat formed by the planar surface segment 142 of the segmented roller 42 and the bottom of the mail stack 20. Furthermore, if the segmented roller 42 is late in starting its motion cycle, the incoming mailpiece 10 may lose its momentum as it reaches the end of the throat.
Thus, it is advantageous and desirable to provide a method and device in an on-edge stacker to improve the performance thereof.